The lgr;=3371 Aring; spectral band of theCthinsp;3Pgr;urarr;Bthinsp;3Pgr;g(vprime;=0,vPrime;=0) second positive system is investigated using timehyphen;resolved spectroscopy with electron beam pulse widths of 100 nsec, 260 nsec, and 5 mgr;sec. Lifetime data for thevprime;=0 vibrational level of theCthinsp;3Pgr;uelectronic state are obtained for incident electron energies and N2gas pressures in the range 25ndash;200 eV and 2ndash;380 mtorr, respectively. In the case of the 260 nsec electron pulse, a single radiative decay component is observed which exhibits a dependence upon electron impact energy. However, in the case of a 5 mgr;sec excitation pulse the resulting radiative decay is observed to consist of two decay components. The shorthyphen;lived component is identified as the primaryCthinsp;3Pgr;ustate excitation, while the longhyphen;lived component is identified as the radiative cascade contribution from higher electronic states, including possibly the metastableEthinsp;3Sgr;+gstate. When the longhyphen;lived cascade contribution is subtracted from the totalCthinsp;3Pgr;upopulation, theCstate natural radiative lifetime becomes independent of energy. In addition, the lifetime is observed to be independent of N2gas pressure over the pressure range sim;2ndash;380 mtorr.
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